The present invention relates to novel compositions of matter which are derivatives of prostacyclin or PGI.sub.2. The chemical name for prostacyclin is (5Z)-5,6-didehydro-9-deoxy-6,9.alpha.-epoxy-PGF.sub.1 .alpha.. Specifically the present invention relates to PGI.sub.2 lower alkyl esters.
Prostacyclin itself was first reported as "PGX" by Moncada and his co-workers. See Moncada, et al., Prostaglandins 12:658-713 (1976). Prostacyclin is a circulating hormone in the arterial circulation of mammals. See "Prostacyclin As A Circulating Hormone", Nature 273:767-768 (29 June 1978) and Grycleweski, R. J., et al., "Generation of Prostacyclin By Lungs In Vivo And Its Release Into Arterial Circulation", Nature 273:765-767 (29 June 1978).